Ākāśa, the sky, with its firmament dotted with stars, planets and other celestial objects has often provided the poets with inspiration to sing. The philo-sophers however have looked at it from an entirely different angle. Is it empty space, a hollow vacuum? Or, is it a material substance, however fine and subtle it may be?
As in the case of other subjects of philosophical enquiry, here also various viewpoints have emerged.
In Jaina metaphysics, ākāśa is consi-dered as space, eternally existing. Its function is to afford room for the existence of all astikāyas or extended substances. Jīvas (souls), pudgala (matter), dharma and adharma (substances responsible for mobility and immobility)—all exist in ākāśa. It is too subtle to be perceived by the senses. Its existence has to be inferred. It is of two kinds—lokākāśa (space contain-ing the world of souls and matter) and alokākāśa (empty space beyond such world).
In the Vaiśeṣika system ākāśa is considered as a dravya or substance, one of its nine kinds. It is the all-pervading substratum of the quality of sound.
The Sāṅkhya, the Yoga and the Vedānta systems consider ākāśa as one of the five tanmātras (potential elements or generic substances) pertaining to sound. The ākāśa that is experienced by us (it is one of the pañcamahābhūtas or five elements) is formed by these tanmatras by the process of pañcīkaraṇa or quintupli-cation. (See PAÑCĪKARAṆA for details.)
According to the process of creation as described in the Upaniṣads, ākāśa is the first of the five bhūtas or elements that emerge out of the Ātman (Taittirīya Upaniṣad 2.1).
The Upaniṣads have sometimes used the word ākāśa for Brahman also (vide Chāndogya Upaniṣad 1.9.1).